We propose to isolate, purify and characterize the proteins of eukaryotic (rat liver) ribosomes. Studies will be carried out on the chemical modification of ribosomal proteins: the identity of ribosomal proteins phosphorylated in vivo and the function of that process; the isolation and characterization of an enzyme that catalyzes the transfer of the gamma-phosphoryl group of GTP to ribosomal proteins; the use of protein kinase-ATP to identify ribosomal subunit interface proteins. We intend to prepare antibodies to ribosomes, ribosomal subunits, and mixtures of ribosomal proteins and use them to: determine the pool of free ribosomal proteins in the cytoplasm; determine structural and functional homologies between prokaryotic and eukaryotic ribosomal proteins; analyze the structure (topography) of the ribosome; and determine the function of individual proteins.